Model Output Discussion - 23rd Jan - 12z onwards

[Geordiesnow]

The updated 96 and 120 hrs fax charts are a one way ticket to troughs-ville.

 

96..fax96s.gif  120..PPVO89.gif

 

Question will be, will they be cold enough for snow? I think its fairly certain the initial blast will be cold enough for snow(away from locations at and close to western coasts)  on Wednesday and into Thursday but if the centre of the lows are too close to the East for Saturday then I'm afraid it looks very very marginal indeed because of the mild sectors.

[Timmytour]

Could be a split vortex in fi , could be very interesting keep watching over Greenland , if we can pull that that vortex northwest we could be in a prime location for some deep cold .image.jpg

Edit: yuk or maybe not ! But to be expected I suppose the mods will always flatten out the pattern in fi .

Some good upgrades today as the days worn on . Be nice to get some cold and snow to low ground for the first time widely for a long old time .

Poor old mods....as if they don't have the work cut out already dealing with this place , now they're given the blame for flattening out the ridge!!

[Cheshire Freeze]

At 264 hrs we're beginning to see vertical advection on the western periphery of the high. As C pointed out earlier, it has retrogression written all over it in the long run (on this particular run).

[Snowy L]

Hopefully this is wave 2 forming in FI. 12z hinted at it, but we really need a split vortex for that final knockout blow.

[Captain Shortwave]

Decent run by the GFS again, the polar flow develops more cleanly and arrives earlier during the weekend. It again ends around the day 9/10 mark with heights building over the UK.

 

The high isn't badly placed to be honest and as others mention can offer possibilities moving forward. 

One good thing about this run is that I can use the word "snizzle"

Edited January 26, 2015 by Captain shortwave

[goosey007]

Well these precipitation must be well wide of the mark for the south as the forecasts I have seen on the BBC and met in no way reflect them .......confused...help somebody?

[East_England_Stormchaser91]

Very interesting end to the run, as an omega type block is modelled more or less over Western Scandi and looks to be retrogressing somewhat and dragging in a cold pool from the East. 

Very interesting synoptics/solutions on the way I feel !! Heres to a Fantastic February 

[Nick F]

The updated 96 and 120 hrs fax charts are a one way ticket to troughs-ville.

96..fax96s.gif 120..

PPVO89.gif

Lol. Bit of trough tourrets from the Duty Forecaster at T+96!

Back to the GFS, some pretty cold advection south across the UK aloft at 500mb early next week, -35C or lower T500s, -40C just north of Scotland. This is kind of gets us into polar disturbance/low development territory to the north of the UK with a northerly lasting a few days or more. Obviously these can't be forecast until much much nearer, only 6-12hrs advance lead time at times using satellite imagery to pick out the comma shape convective clusters, but conditions would be ripe with those sort of upper temp profiles to the north of the UK.

Edited January 26, 2015 by Nick F

[Chris K]

Well these precipitation must be well wide of the mark for the south as the forecasts I have seen on the BBC and met in no way reflect them .......confused...help somebody?

 

To be honest, I don't use those charts for precipitation forecasts. They are OK at seeing the general trend but I find they become less helpful when pinning local details and stick to the higher resolution models when it gets in range. If you do not have access to these higher resolution models, stick with Met Office fax charts and precipitation forecasts etc..but even these will change! (I also look at the EURO4 model that you should be able to get on - that tends to be useful to!)

 

For example - the charts you posted at first glance looks like a lot..but actually you'll probably find it's showers around the coasts with some reaching inland along surface based troughs and fronts. Parts of Ireland, Wales and Scotland could do particularly well though!

Edited January 26, 2015 by Chris K

[goosey007]

To be honest, I don't use those charts for precipitation forecasts. They are OK at seeing the general trend but I find they become next to useless when pinning local details and stick to the higher resolution models when it gets in range. If you do not have access to these higher resolution models, stick with Met Office fax charts and precipitation forecasts etc..but even these will change! 

 

For example - the charts you posted at first glance looks like a lot..but actually you'll probably find it's showers around the coasts with some reaching inland along surface based troughs and fronts.

Thanks for the reply Chris ......yeah I understand these charts are only a rough guide just didn't realise how rough!

[Timmytour]

interesting listening to the weather channel now as they describe the developing situation over the East Coast of the States. lots of expectation that New York is going to be hit by a further foot of snow 9it already has five inches) but the guy did say there's some divergence in what the models are showing..with some not giving them too much more!

It made me think that (apart from demonstrating how even short term forecasting of snow can be fraught with difficulty) that there's a lot of butterflies flapping thier wings upstream which could impact on what the models show us in future runs, be that difference positive or negative on our chances of a long spell

[Paul_1978]

OK! OK! We get that you've found a new word!!! You've used it in loads of posts these last few days!!!!!

Not as annoying as the over-use in here of the word "juncture"!

[The Enforcer]

stick to the higher resolution models when it gets in range.

Good point, what say you, Mr Hi-Res?

 

http://www.meteociel.fr/modeles/wrfnmm.php?ech=3&mode=1&map=5

 

 

At least it will be updating shortly.

[MR EXTREMES]

Lol. Bit of trough tourrets from the Duty Forecaster at T+96!

Back to the GFS, some pretty cold advection south across the UK aloft at 500mb early next week, -35C or lower T500s, -40C just north of Scotland. This is kind of gets us into polar disturbance/low development territory to the north of the UK with a northerly lasting a few days or more. Obviously these can't be forecast until much much nearer, only 6-12hrs advance lead time at times using satellite imagery to pick out the comma shape convective clusters, but conditions would be ripe with those sort of upper temp profiles to the north of the UK.

And there's a very strong possibility of thunder snow now that would be exciting.

Good to see winter paying us a visit the models have been very consistent and have moved away from the recent rattles.

Shovel still on standby!.

I think more suprises to come this week into the weekend.

[Chris K]

Thanks for the reply Chris ......yeah I understand these charts are only a rough guide just didn't realise how rough!

 

Just to add - I'm not saying they are totally useless - It's just that being "zoomed out" like the ones you posted makes it a bit difficult to forecast where any rain/snow might fall exactly.

 

The Netweather chart viewer is better. Example - take Weds 1200hrs...just before the 1300 hrs chart you linked.

 

So a similar looking "Precipitation type" chart...but when looking at 'actual' Precipitation it's gives a better view for potential shower activity. From that it looks like exposed N/NW and some W coasts could see a fair number of showers. Be aware that other factors will affect whether it's likely to fall as rain/sleet or snow. I'm sure you know this though

Edited January 26, 2015 by Chris K

[Biggin]

The updated 96 and 120 hrs fax charts are a one way ticket to troughs-ville.

 

96..fax96s.gif  120..PPVO89.gi

Liking troughs, from an imby perspective, can only be an good sign

[Chief Wiggam]

Just watched (twice) the South Today extended forecast and it bears very little relationship to what is being discussed here. Only Daily Excess stylee doomwatch aspect.... "very cold on Saturday"

[geordiekev]

Just a quick question regarding the NH profile going forward. In reference to the Usa deep freeze forecasted which bearly gets above 0c until 26th FEBRUARY. I know it's possibly a myth that when the deep cold sets in, it is difficult to shift which seems the case for New York forecast for a WHOLE MONTH from today.

Would the stagnant system in U.S. prevent lows pushing over the Atlantic and maybe the reason models are showing an Atlantic block which may aid retrogression and possibly provide the holy grail that is the omega block in the mid Atlantic?

I could be way off mark, as obviously many other factors but would be interesting to have the views of the respected round table members in here.

Edited January 26, 2015 by geordiekev

[goosey007]

Just to add - I'm not saying they are totally useless - It's just that being "zoomed out" like the ones you posted makes it a bit difficult to forecast where any rain/snow might fall exactly.

 

The Netweather chart viewer is better. Example - take Weds 1200hrs...just before the 1300 hrs chart you linked.

prectypeuktopo.png

ukprec.png

 

So a similar looking "Precipitation type" chart...but when looking at 'actual' Precipitation it's gives a better view for potential shower activity. From that it looks like exposed N/NW and some W coasts could see a fair number of showers. Be aware that other factors will affect whether it's likely to fall as rain/sleet or snow. I'm sure you know this though

Looks very marginal then particularly for the dreaded M4 corridor south ! I will assume the hi res models take into account all the other factor I.e height depths dam's etc cheers

[Trom]

Just watched (twice) the South Today extended forecast and it bears very little relationship to what is being discussed here. Only Daily Excess stylee doomwatch aspect.... "very cold on Saturday"

 

No unfortunately for the far South it looks slightly the wrong side of marginal but certainly a never say never scenario.  I'd say sledging with the kids would be an unexpected bonus for London.  The rest of the country looks set for a week of cold.  The ensembles for London are showing remarkable consistency for temps out to the 4th/5th of Feb - 9-10 days.  

 

With some notable posters missing today there's been a slight lack of analysis of the drivers behind the models.  Tamara's post was a good read earlier https://forum.netweather.tv/topic/82366-model-output-discussion-23rd-jan-12z-onwards/page-46

Edited January 26, 2015 by Trom

[Chris K]

Looks very marginal then particularly for the dreaded M4 corridor south ! I will assume the hi res models take into account all the other factor I.e height depths dam's etc cheers

 

Yes, but surprises can pop up. All depends on developments in the close time range We are seeing some decent charts at the moment so hopefully they continue, so that it might allow us a chance of seeing something   It will be feeling cold that's for sure...

Edited January 26, 2015 by Chris K

[bryan629]

Question will be, will they be cold enough for snow? I think its fairly certain the initial blast will be cold enough for snow(away from locations at and close to western coasts)  on Wednesday and into Thursday but if the centre of the lows are too close to the East for Saturday then I'm afraid it looks very very marginal indeed because of the mild sectors.

Hi GS .... if you look closely enough at the fax chart (AT T+96) you will notice the 0 degree isotherm is dangling somewhere abouts in Northern Spain,...(just about where the PFJ GOES)  in the meantime look closely at the fax chart and you will see the 528 dam line has cleared the south coast into northern France. im sure you know that any precipitation that falls out of the sky north of the 528 dam line is of the white stuff right down to sea level.

its defo a case of nowcasting as Nick L alluded to in his post above.

Edited January 26, 2015 by bryan629

[The Enforcer]

Looks very marginal then particularly for the dreaded M4 corridor south ! I will assume the hi res models take into account all the other factor I.e height depths dam's etc cheers

Euro4 only going as far as 6pm Weds - bone dry over much of England: http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=ukuk&MODELL=euro4&MODELLTYP=1&BASE=-&VAR=prty&HH=48&ZOOM=0&WMO=&ARCHIV=0&RES=0

 

Still waiting for NMM to update, which will extend coverage to 6pm Thurs.

 

Just watched (twice) the South Today extended forecast and it bears very little relationship to what is being discussed here. Only Daily Excess stylee doomwatch aspect.... "very cold on Saturday"

Points West get a proper meteorologist, whereas on South Today they are more interested in looking at pretty photos viewers have sent in. The presenter will say something like, "but it'll be brighter on Sunday" and the graphic for Sunday will show heavy rain.

Edited January 26, 2015 by The Enforcer

[Frosty.]

Nice way to finish Monday night from 18z, plenty of snow showers to look forward to from midweek onwards and a potent Northerly from the weekend until at least the middle of next week, haven't had a decent northerly for 5 years so here's hoping for that and for a better 0z than this morning.

[Geordiesnow]

Hi GS .... if you look closely enough at the fax chart (AT T+96) you will notice the 0 degree isotherm is dangling somewhere abouts in Northern Spain,...(just about where the PFJ GOES)  in the meantime look closely at the fax chart and you will see the 528 dam line has cleared the south coast into northern France. im sure you know that any precipitation that falls out of the sky north of the 528 dam line is of the white stuff right down to sea level.

its defo a case of nowcasting as Nick L alluded to in his post above.

 

Yes however the FAX charts tends to mirror the UKMO output which i mentioned a few times that its the best regarding reducing any milder sector as the main core of the trough(low pressure system) is far enough eastwards hence you get a quicker Northerly, less of a mild sector and the colder air filters down quicker. 

 

ECM and GFS has the trough too close to us so you get those pesky mild sectors coming into play before the cold air finally makes its way southwards.